The invention relates generally to catheters, and more particularly to a catheter having a steerable dual-profile distal-end region.
The heart beat in a healthy human is controlled by the sinoatrial node (xe2x80x9cS-A nodexe2x80x9d) located in the wall of the right atrium. The S-A node generates electrical signal potentials that are transmitted through pathways of conductive heart tissue in the atrium to the atrioventricular node (xe2x80x9cA-V nodexe2x80x9d) which in turn transmits the electrical signals throughout the ventricle by means of the His and Purkinje conductive tissues. Improper growth of, or damage to, the conductive tissue in the heart can interfere with the passage of regular electrical signals from the S-A and A-V nodes. Electrical signal irregularities resulting from such interference can disturb the normal rhythm of the heart and cause an abnormal rhythmic condition referred to as xe2x80x9ccardiac arrhythmia.xe2x80x9d
While there are different treatments for cardiac arrhythmia, including the application of anti-arrhythmia drugs, in many cases ablation of the damaged tissue can restore the correct operation of the heart. Such ablation can be performed by percutaneous ablation, a procedure in which a catheter is percutaneously introduced into the patient and directed through an artery or vein to the atrium or ventricle of the heart to perform single or multiple diagnostic, therapeutic, and/or surgical procedures. In such case, an ablation procedure is used to destroy the tissue causing the arrhythmia in an attempt to remove the electrical signal irregularities or create a conductive tissue block to restore normal heart beat or at least an improved heart beat. Successful ablation of the conductive tissue at the arrhythmia initiation site usually terminates the arrhythmia or at least moderates the heart rhythm to acceptable levels. A widely accepted treatment for arrhythmia involves the application of RF energy to the conductive tissue.
In the case of atrial fibrillation (xe2x80x9cAFxe2x80x9d), a procedure published by Cox et al. and known as the xe2x80x9cMaze procedurexe2x80x9d involves continuous atrial incisions to prevent atrial reentry and to allow sinus impulses to activate the entire myocardium. While this procedure has been found to be successful, it involves an intensely invasive approach. It is more desirable to accomplish the same result as the Maze procedure by use of a less invasive approach, such as through the use of an appropriate electrophysiological (xe2x80x9cEPxe2x80x9d) catheter system.
One such EP catheter system, as disclosed in U.S. Pat. Nos. 6,059,778 and 6,096,036, includes a plurality of spaced apart band electrodes located at the distal end of the catheter and arranged in a linear array. The band electrodes are positioned proximal heart tissue. RF energy is applied through the electrodes to the heart tissue to produce a series of long linear lesions similar to those produced by the Maze procedure. The catheters currently used for this procedure are typically flexible at the distal end, and the profile at the distal end is adjustable. However, when using such catheters, it is often difficult to conform the distal-end profile to some of the irregular topographies of the interior cavities of the heart. In other instances, it is difficult for a multi-electrode catheter that is designed to produce long linear lesions to access and ablate tissue in regions that require short linear lesions, such as the so-called isthmus region that runs from the tricuspid annulus to the eustachian ridge. Ablation of tissue in this region, and other regions non-conducive to the placement of multi-electrode, long, linear-lesion ablation catheters within them, is best accomplished by delivering RF energy to a tip electrode to produce localized spot lesions or if longer lesions are required, by energizing the tip while it is moved across the tissue.
Other catheters for producing spot lesions or tip-drag lesions typically comprise a tip ablation electrode and a plurality of mapping band electrodes positioned at the distal end of the catheter. The catheters are steerable in that they are configured to allow the profile of the distal end of the catheter to be manipulated from a location outside the patient""s body. Steerable catheters that produce multiple deflection profiles of their distal ends provide a broader range of steerability. However, known steerable catheters such as that disclosed in U.S. Pat. No. 5,195,968 have steering tendons attached to a ribbon, at or near the longitudinal centerline of the catheter. Because of the relatively short distance between the tendon attachment point and the ribbon that resides along the centerline of the catheter sheath, a force applied to the tendon results in a relatively small bending moment for deflecting the distal tip. The ribbon/tendon assembly is typically provided clearance to allow the tendon to become substantially displaced from the centerline as deflection progresses, thereby enlarging the moment arm and consequently increasing the applied bending moment. Unfortunately, this requires such designs to include additional lumen space, translating into larger catheter diameters. Larger diameter catheters are undesirable due to the increased trauma they inflict on a patient. Further, as the tendon displaces to the extent that it contacts the catheter wall, the associated friction may necessitate greater exertion to further deflect the distal tip. Lessening the amount of force required to deflect the distal tip of a catheter by actions outside the catheter is desired in that the catheter tip can more easily be deflected and placed in the correct location within a patient.
Hence, those skilled in the art have identified a need for a tip-electrode, ablation catheter with a steerable distal-end region that is capable of accessing those areas of the heart which are typically inaccessible by multi-electrode ablation catheters. Needs have also been identified for smaller diameter catheters to improve patient comfort and for more easily deflected catheters so that they may be more easily used. The present invention fulfills these needs and others.
Briefly, and in general terms, the present invention is directed to a catheter with a steerable multiple-profile distal-end region.
In a first aspect, the invention relates to a catheter that includes a sheath having a proximal region and a distal-end region. The catheter also includes a first steering tendon that is housed within the sheath. The first steering tendon has a first end attached to the distal-end region at a point proximate an inner surface of the sheath, and a second end located at the proximal region of the sheath. Movement of the first steering tendon in a proximal direction causes the sheath distal-end region to deflect. The catheter also includes a second steering tendon that is housed within the sheath. The second steering tendon has a first end attached to the distal-end region at a point proximate the inner surface of the sheath, and a second end located at the proximal region of the sheath. Movement of the second steering tendon in the proximal direction causes the sheath distal-end region to deflect.
By having the distal ends of the steering tendons located offset from the centerline and proximate the inner surface of the sheath, the bending moments of the steering tendons are increased. Thus, a relatively low amount of force is required to displace the steering tendons in order to deflect the distal-end region.
In a detailed aspect of the invention, the attachment point of the first steering tendon is distal the attachment point of the second steering tendon. In another detailed facet, the attachment point of the first steering tendon and the attachment point of the second steering tendon are axially aligned. In yet another detailed aspect, the attachment point of the first steering tendon and the attachment point of the second steering tendon are angularly aligned. In still another detailed facet, the attachment point of the first steering tendon and the attachment point of the second steering tendon are angularly displaced from each other. In further detailed facets, the angular displacement between the attachment points is approximately 90xc2x0 or 180xc2x0.
In a second aspect, the invention relates to a catheter that includes a sheath having a proximal region and a distal-end region. The catheter also includes a first steering tendon that is housed within the sheath. The first steering tendon has a first end attached to the distal-end region at a point proximate an inner surface of the sheath, and a second end located at the proximal region of the sheath. Movement of the first steering tendon in a proximal direction causes the sheath distal-end region to deflect. The catheter also includes a second steering tendon that is housed within the sheath. The second steering tendon has a first end attached to the distal-end region at a point proximate the inner surface of the sheath, at a point proximal to the attachment point of the first steering tendon, and a second end located at the proximal region of the sheath. Movement of the second steering tendon in the proximal direction causes the sheath distal-end region to deflect.
In a detailed aspect of the invention, there is a distal tip attached to the distal end of the distal-end region, and the first steering tendon is secured within the distal tip. In another detailed facet, the attachment point of the first steering tendon and the attachment point of the second steering tendon are angularly aligned with each other. In yet another detailed aspect, the attachment point of the first steering tendon and the attachment point of the second steering tendon are angularly displaced from each other. In still another detailed facet, the angular displacement between the attachment points is approximately 90xc2x0 or 180xc2x0. In a further detailed aspect, an anchor band is positioned within the distal-end region, proximal the distal tip, and the first end of the second steering tendon is attached to the anchor band. In yet anther detailed facet, the first end of the second steering tendon is attached to the inner surface of the anchor band.
In a third aspect, the invention relates to a catheter for use with biological tissue. The catheter includes a sheath having a proximal region and a distal-end region, and at least one electrode that is located in the distal-end region for transferring energy to the biological tissue. The catheter also includes a first steering tendon that is housed within the sheath. The first steering tendon has a first end attached to the distal-end region at a point proximate an inner surface of the sheath, and a second end exiting a proximal end of the sheath. Movement of the first steering tendon in a proximal direction causes the sheath distal-end region to deflect. The catheter also includes a second steering tendon that is housed within the sheath. The second steering tendon has a first end attached to the distal-end region at a point proximate the inner surface of the sheath, at a point proximal to the attachment point of the first steering tendon, and a second end exiting the proximal end of the sheath. Movement of the second steering tendon in the proximal direction causes the sheath distal-end region to deflect.
In a fourth aspect, the invention relates to a catheter that includes a sheath having a proximal region, a distal-end region, and a longitudinal centerline. The catheter also includes a first steering tendon that is housed within the sheath. The first steering tendon has a first end attached to the distal-end region at a location offset from the centerline of the sheath, and a second end exiting a proximal end of the sheath. Movement of the first steering tendon in a proximal direction causes the sheath distal-end region to deflect. The catheter also includes a second steering tendon that is housed within the sheath. The second steering tendon has a first end attached to the distal-end region at a location offset from the centerline of the sheath, and a second end exiting the proximal end of the sheath, wherein movement of the second steering tendon in the proximal direction causes the sheath distal-end region to deflect.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings, which illustrate by way of example the features of the invention.